Heretofore, in a glass melting furnace, a glass product is produced by burning a fuel such as heavy oil by means of air, whereby there has been a problem that during such burning, nitrogen in air becomes nitrogen oxides (NOx) in a high temperature state.
In recent years, as a glass melting furnace to solve such a problem, attention has been drawn to a so-called full oxygen-fuel combustion glass melting furnace, wherein a fuel is burned by means of oxygen gas i.e. a gas containing oxygen in an amount of at least 99 vol %. In the full oxygen-fuel combustion glass melting furnace, nitrogen present during combustion of the fuel decreases substantially, and consequently, the amount of NOx in the combustion gas likewise substantially decreases.
However, even in such a case, nitrogen present during combustion of the fuel will not be 0. Namely, there will be nitrogen contained in air leaked into the furnace from the atmospheric air outside the furnace, nitrogen attributable to a nitrogen compound contained in the fuel, or nitrogen contained as an impurity in the oxygen gas to be used for combustion. It is desired to reduce NOx in a combustion gas attributable to such nitrogen.
Further, in a case where a nitrate is used as a raw material for glass, NOx will be formed by the decomposition of the nitrate raw material.
It is difficult to reduce such NOx even by a full oxygen-fuel combustion glass melting furnace wherein a fuel is burned by means of oxygen gas rather than air.
It is an object of the present invention to provide a method for reducing NOx in a combustion gas discharged from a combustion furnace wherein a fuel is burned by means of a gas containing oxygen in an amount of at least 80 vol %, such as oxygen gas.